Patent Literature 1 discloses a technology in which when accelerator opening degree Acc is less than predetermined first opening degree threshold value Aref1, it is judged that the accelerator opening degree Acc is sufficiently small and an energy efficiency of the vehicle is in a good state, and an ECO indicator is lighted up, whereas when the accelerator opening degree Acc is not less than predetermined second opening degree threshold value Aref2, it is judged that the accelerator opening degree Acc is too large and an energy efficiency of the vehicle is not in the good state, and the ECO indicator is extinguished. In addition, the Patent Literature 1 discloses that in a case where the accelerator opening degree Acc is not less than the predetermined first opening degree threshold value Aref1 and is less than predetermined second opening degree threshold value Aref2, if accelerator opening speed Va is less than predetermined opening speed threshold value Varef, it is judged that accelerator operation is good and an energy efficiency of the vehicle is in a good state, and the ECO indicator is lighted up, whereas in a case where the accelerator opening degree Acc is not less than the predetermined first opening degree threshold value Aref1 and is less than the predetermined second opening degree threshold value Aref2, if the accelerator opening speed Va is not less than the predetermined opening speed threshold value Varef, it is judged that accelerator operation is not good and an energy efficiency of the vehicle is not in the good state, and the ECO indicator is extinguished.
In a vehicle equipped with a manual transmission or a vehicle that is running in a so-called sport mode or a manual mode of an automatic transmission, fuel economy is enhanced by carrying out a shift-up operation when vehicle speed is increased by depressing an accelerator pedal, but fuel economy is deteriorated when a gear position (gear ratio) is retained without carrying out the shift-up operation.
In the above-described Patent Literature 1, the first opening degree threshold value Aref1 and the second opening degree threshold value Aref2 which are used upon judging turn-on/turn-off of the ECO indicator are set to increase as the vehicle speed becomes higher.
Specifically, in a case where the gear position (gear ratio) is retained without carrying out the shift-up operation when the vehicle speed is increased by depressing the accelerator pedal, as the vehicle speed becomes higher, the first opening degree threshold value Aref1 for lighting the ECO indicator is increased so that light-up of the ECO indicator is more facilitated. Therefore, there occurs such a fear that even when fuel economy is actually deteriorated, the ECO indicator is occasionally lighted up, so that a vehicle operator may be urged toward deterioration in fuel economy.